<ol>
  <li>Choose the direction of the arc in the options toolbar.</li>
  <li>Set the center of the arc using the mouse or enter a coordinate in the
  command line.</li>
  <li>Define the radius by clicking a point on the arc or by entering a
  coordinate into the command line. You may also enter the radius in
  the command line.</li>
  <li>Set the start angle with the mouse or by entering a coordinate or the
  angle in the command line.</li>
  <li>Set the end angle the same way as the start angle.</li>
</ol>
